grade 10 math?! please help?

1. The surface area of a sphere is: SA =

If the surface area of the sphere is 113.1 cm2calculate the radius.

2.Sebastian ran a mile race at the Portland relays in a time of 4 minutes 20 seconds.He then ran a 1500 metre race in Kamloops, British Columbia in a time of 3 minutes. His average speed was faster in Kamloops than Portland. True or false?

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  • Big D
    Lv 4
    8 years ago

    surface area of a sphere = 4*pi*r^2

    113.1 = 4*3.14*r^2

    r^2 = 9.00

    r = 3 cm

    he ran in Portland 5280 feet in 260 seconds for an average speed of 20.3 feet per second

    then he ran in Kamloops 1500*3.28 feet or 4920 feet in 180 seconds for an average speed of 27.3 ft/s

    true

  • 8 years ago

    1. SA=4 pi r2 ( ie radius squared)

    113.1 = 4*3.17 r2

    113.1 = 12.57 * r2

    r2 = 8.997 (approx$

    Now you work out value of t

    2. Not 100% sure but I'd say false as the first race is relay and scone isn't so I can't tell if he ran faster or slower in his part of relay

    Source(s): Personal knowledge
  • 8 years ago

    1)SA=4(pi)r^2 R=Squareroot(SA/4pi)

    R=squareroot(113.1/4pi)=3

    2) First you need to put everything into the same units

    1m=3.281ft

    1500m=4921.26ft

    1609.34=1mile=5280ft

    Then find average speed of both

    4921.26/((4*60)+20)=18.93ft/sec

    5280/(3*60)=29.33ft/sec

    so the statement is true

  • 8 years ago

    surface area of sphere is 4 * pi * r^2 :

    So 113 = 4 * pi * r^2

    113/4 = pi * r2^

    113/(4*pi) = r^2

    r= sqrt(113/(4*pi))

    r = sqrt(9) = 3

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  • Anonymous
    8 years ago

    1.radius is 3.000796073 or 3

    2.true

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